Method and apparatus for cooling reduced-iron agglomerate

ABSTRACT

In a method and an apparatus for cooling a reduced-iron agglomerate in a reduced-iron agglomerate production equipment wherein an iron oxide agglomerate is reduced in a reducing furnace and discharged as a reduced-iron agglomerate, a conveyer to convey said reduced-iron agglomerate is installed at the outlet of said reduced-iron agglomerate production equipment, a plurality of spray nozzles are installed above, or above and below, said conveyer at intervals in the conveying direction of said reduced-iron agglomerate, and said reduced-iron agglomerate on said conveyer is cooled intermittently by ejecting cooling water, continuously or intermittently, through said spray nozzles.

TECHNICAL FIELD

The present invention relates to a method and an apparatus for cooling ahigh-temperature reduced-iron agglomerate that is reduced in, anddischarged continuously from, a reducing furnace, in reduced-ironproduction equipment, to produce a reduced-iron agglomerate from an ironoxide agglomerate.

Here, the above method and apparatus include, for example, a method andan apparatus for cooling a reduced-iron agglomerate produced in a rotaryhearth furnace, for reduction, wherein a reduced iron is produced byprocessing dust and sludge containing metallic oxide generated in themetal refining industry and the metal processing industry.

BACKGROUND ART

As a method for cooling a reduced-iron agglomerate discharged from areduced-iron production equipment, a method has heretofore been put intopractical use wherein a reduced-iron agglomerate is immersed and cooledin a water bath, thereafter taken out from the water bath with aconveyer, discharged directly to an earth floor and stored in stacks,and then, according to circumstances, conveyed and charged into anelectric arc furnace.

However, the reduced-iron agglomerate produced by this immersing andcooling method has a high water content and, when it is charged directlyinto molten metal, there is the danger of a water vapor explosion.Therefore, it has been used only for charging into an electric arcfurnace. Moreover, the reduced-iron agglomerate has the problems ofpulverization and reoxidation.

Japanese Patent No. 3145834 discloses a method for producingreduced-iron briquettes wherein reduced iron produced by a directreduction ironmaking method is formed into briquettes by a briquettemachine and the reduced-iron briquettes are cooled slowly, at a coolingrate of 150 to 250° C./min., with a water spray.

However, this method is a method wherein high-temperature reduced-ironbriquettes are cooled slowly with a water spray in order to suppresscracking of the reduced-iron briquettes and not a method wherein areduced-iron agglomerate discharged from a reduced-iron productionequipment, such as a rotary hearth furnace, is cooled. Moreover, thismethod does not take an appropriate water content of the reduced-ironagglomerate into consideration.

Further, Japanese Patent No. 3009661 discloses a method whereinhigh-temperature reduced-iron briquettes having been heated and reducedare cooled with water so that an average cooling rate may be in therange from 1,500 to 500° C./min. during the time when the surfacetemperature decreases from 650° C. to 150° C.

However, this method is one that is related to the cooling ofreduced-iron pellets that are different in size and features from anagglomerate such as briquettes as intended in the present invention.Therefore, this method cannot be applied as it is.

In addition, though the temperature of a reduced-iron agglomeratedischarged from a rotary hearth furnace is about 1,000° C., the patentdescribes neither a cooling method and a cooling rate in the temperatureabove 650° C. nor a concrete cooling means even in the temperature below650° C., and further pays no attention at all to the water content ofagglomerate.

SUMMARY OF THE INVENTION

The object of the present invention is, by solving the aforementionedproblems of prior art, to provide a cooling method and a coolingapparatus for regulating the temperature at the center, and the watercontent, of a reduced-iron agglomerate to appropriate ranges and also toprovide the following concrete means for solving the technologicalproblems: to suppress the reoxidation of a reduced-iron agglomeratecaused by the atmospheric air by means of rapidly cooling thereduced-iron agglomerate, at about 1,000° C., discharged from areduced-iron production equipment such as a rotary hearth furnace to atemperature below 300° C.; to make it possible to charge thereduced-iron agglomerate into molten metal, to decrease the waterevaporation energy during melting by means of controlling the watercontent of the reduced-iron agglomerate after the cooling to 6% or less;and to suppress the pulverization and the reoxidation of thereduced-iron agglomerate by means of optimizing a cooling time.

The present invention solves the aforementioned problems and the gist ofthe present invention is as follows;

(1) A method for cooling a reduced-iron agglomerate in a reduced-ironagglomerate production equipment wherein an iron oxide agglomerate isreduced in a reducing furnace and discharged as a reduced-ironagglomerate characterized by:

-   -   installing a conveyer to convey said reduced-iron agglomerate at        the outlet of said reduced-iron agglomerate production        equipment;    -   installing a plurality of spray nozzles above or above and below        said conveyer at intervals in the conveying direction of said        reduced-iron agglomerate; and    -   cooling said reduced-iron agglomerate on said conveyer        intermittently by ejecting cooling water continuously through        said spray nozzles.

(2) A method for cooling a reduced-iron agglomerate in a reduced-ironagglomerate production equipment wherein an iron oxide agglomerate isreduced in a reducing furnace and discharged as a reduced-ironagglomerate characterized by:

-   -   installing a conveyer to convey said reduced-iron agglomerate at        the outlet of said reduced-iron agglomerate production        equipment;    -   installing a plurality of spray nozzles above or above and below        said conveyer at intervals in the conveying direction of said        reduced-iron agglomerate; and    -   cooling said reduced-iron agglomerate on said conveyer        intermittently by ejecting cooling water intermittently through        said spray nozzles so that an ejecting time T1 and an ejection        stopping time T2 may satisfy the following expression (1),        1.2×T1≦T1+T2≦10×T1  (1),        where, T1 is an ejecting time and T2 an ejection stopping time.

(3) A method for cooling a reduced-iron agglomerate in a reduced-ironagglomerate production equipment wherein an iron oxide agglomerate isreduced in a reducing furnace and discharged as a reduced-ironagglomerate characterized by:

-   -   installing a conveyer to convey said reduced-iron agglomerate at        the outlet of said reduced-iron agglomerate production        equipment;    -   installing a plurality of spray nozzles above said conveyer;    -   spraying cooling water through said spray nozzles on said        reduced-iron agglomerate on said conveyer; and    -   accumulating said cooling water so as to form a water layer 1 mm        to less than 10 mm, in depth, on said conveyer.

(4) An apparatus for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

-   -   a conveyer to convey said reduced-iron agglomerate at the outlet        of said reduced-iron agglomerate production equipment; and    -   a plurality of spray nozzles above or above and below said        conveyer at the intervals of P, satisfying the following        expression (2), in the conveying direction of said reduced-iron        agglomerate in order to cool said reduced-iron agglomerate on        said conveyer intermittently by ejecting cooling water        continuously through said spray nozzles,        1.2×B≦P≦10×B  (2),        where, B is the spread width of cooling water in the conveying        direction and P is the intervals of installed spray nozzles.

(5) An apparatus for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

-   -   a conveyer to convey said reduced-iron agglomerate at the outlet        of said reduced-iron agglomerate production equipment; and    -   a plurality of spray nozzles above or above and below, said        conveyer at intervals in the conveying direction of said        reduced-iron agglomerate and setting the spread width of cooling        water in the conveying direction B and the spread width thereof        in the conveyer width direction W so as to satisfy the following        expression (3) in order to cool said reduced-iron agglomerate on        said conveyer intermittently by ejecting said cooling water        through said spray nozzles,        W≧2×B  (3),        where, W is the spread width of cooling water in the conveyer        width direction and B is the same in the conveying direction.

(6) An apparatus for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

-   -   a conveyer to convey said reduced-iron agglomerate at the outlet        of said reduced-iron agglomerate production equipment; and    -   a plurality of spray nozzles above, or above and below, said        conveyer at the intervals of P, satisfying the following        expression (4), in the conveying direction of said reduced-iron        agglomerate in order to cool said reduced-iron agglomerate on        said conveyer intermittently by ejecting cooling water        intermittently through said spray nozzles,        B≦P  (4),        where, B is the spread width of cooling water in the conveying        direction and P is the intervals of installed spray nozzles.

(7) An apparatus for cooling a reduced-iron agglomerate according to theitem (6), characterized in that said spread width of cooling water inthe conveying direction B and said spread width thereof in the conveyerwidth direction w satisfy the following expression (3),W≧2×B  (3),where, w is the spread width of cooling water in the conveyer widthdirection and B is the same in the conveying direction.

(8) An apparatus for cooling a reduced-iron agglomerate according to anyone of the items (4) to (7), characterized in that said spread width ofcooling water in the conveyer width direction W and the width of saidconveyer CW satisfy the following expression (5),CW≦W  (5),where, CW is the width of a conveyer and W is the spread width ofcooling water in the conveyer width direction.

(9) An apparatus for cooling a reduced-iron agglomerate in areduced-iron agglomerate production equipment wherein an iron oxideagglomerate is reduced in a reducing furnace and discharged as areduced-iron agglomerate characterized by:

-   -   a conveyer to convey said reduced-iron agglomerate at the outlet        of said reduced-iron agglomerate production equipment;    -   a plurality of spray nozzles to spray cooling water on said        reduced-iron agglomerate above said conveyer; and    -   side portions arranged on said conveyer so as to accumulate said        cooling water and form a water layer 1 mm to less than 10 mm, in        depth, on said conveyer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a cooling apparatus according to the presentinvention.

FIG. 2 is a plan view taken on line A-A of FIG. 1.

FIG. 3 is an expanded sectional view being taken on line C-C of FIG. 2and showing an example of water spray according to the presentinvention.

FIG. 4 is a front view taken on line B-B of FIG. 2.

FIG. 5 is a view showing an example of spray nozzles according to thepresent invention.

FIG. 6 is a graph showing the relationship between the spray amount ofcooling water and the temperature at the center of a reduced-ironagglomerate.

FIG. 7 is a graph showing the relationship between the spray amount ofcooling water and the water content of a reduced-iron agglomerate.

FIG. 8 is a graph showing the relationship between the temperature atthe center of a reduced-iron agglomerate and the water content thereof.

FIG. 9 is a view showing an example of a cooling pattern according tothe present invention.

FIG. 10 is a graph showing an example of the temperature change ofagglomerate according to the present invention.

FIG. 11 is a view showing another cooling apparatus according to thepresent invention wherein spray nozzles are installed above and below aconveyer.

FIG. 12 is a view showing a water spraying situation in the coolingapparatus shown in FIG. 11.

FIG. 13 is a view showing a water supply means in the cooling apparatusshown in FIG. 11.

FIG. 14 is a view showing a conventional arrangement of spray nozzles.

FIG. 15 is a view showing another conventional arrangement of spraynozzles.

FIG. 16 is a plan view being taken on line A-A of FIG. 1 and showinganother embodiment according to the present invention.

FIG. 17 is an expanded sectional view being taken on line C-C of FIG. 2and showing another example of water spray according to the presentinvention.

FIG. 18 is a view showing another example of a cooling pattern accordingto the present invention.

FIG. 19 is a view showing another cooling apparatus according to thepresent invention.

FIG. 20 is a view showing the structure of a cooling conveyer.

FIG. 21 is a graph showing the relationship between the spray amount ofcooling water and the temperature at the center of a reduced-ironagglomerate.

FIG. 22 is a graph showing the relationship between the spray amount ofcooling water and the water content of a reduced-iron agglomerate.

THE MOST PREFERRED EMBODIMENT

1) The present invention is explained on the basis of the coolingapparatus shown in FIGS. 1 and 2.

An iron oxide agglomerate is reduced in a rotary hearth furnace 13 usedas a reducing furnace and the reduced-iron agglomerate thus produced isdischarged continuously from an outlet 8 to discharge the reduced-ironagglomerate. The discharged high-temperature reduced-iron agglomerate 5is cooled with water sprayed through a plurality of spray nozzles 1while being conveyed on a conveyer 6 in a cooling apparatus 16 placed inconnection with the outlet 8, then discharged from another outlet 7 todischarge the reduced-iron agglomerate, and conveyed to a storageinstallation, or the like, not shown in the figures.

Each of the spray nozzles 1 is attached at prescribed intervals to anozzle header 2 installed in parallel with the conveying direction of,and above, the conveyer 6.

The spray nozzles 1, the spray header 2 and the conveyer 6 are coveredby a casing 15 and, at the top end of the casing 15, the outlet 7 isplaced to discharge the cooled reduced-iron agglomerate 5 and, at thebottom end thereof, the outlet 9 is placed to discharge sludge formed byspraying water on the reduced-iron agglomerate 5.

FIG. 2 shows a plan view taken on line A-A of FIG. 1 from above theconveyer 6 and the cooling water sprayed through each of the spraynozzles 1 (hereunder referred to as “cooling water” or “spray water” insome cases) is sprayed at intervals so as to form a spread width ofcooling water in the conveying direction “B” as shown by the spray range1-1.

FIG. 3 is an expanded sectional view taken on line C-C of FIG. 2. In thefigure, each of the spray nozzles 1 is attached to the spray header 2 atintervals “P” in the conveying direction and spray water is sprayed atintervals on the conveyer 6 so as to form the spread width of coolingwater in the conveying direction “B”.

FIG. 4 shows a front view taken on line B-B of FIG. 2. In the figure, aspray nozzle 1 is attached to the spray header 2 disposed in the centerof the width direction of the conveyer 6 and spray water is sprayed onthe conveyer 6 so as to form the spread width in the width direction “W”that is larger than the width of the conveyer 6 “CW”.

Water is supplied to the spray header 2 through a feed water pipe 3 asshown in FIG. 5.

As explained above, a cooling apparatus according to the presentinvention is an apparatus that intermittently cools a reduced-ironagglomerate 5 on a conveyer 6 by installing a plurality of spray nozzles1 above the conveyer 6 at intervals in the conveying direction of thereduced-iron agglomerate 5 and ejecting spray water continuously througheach of the spray nozzles. The condition that assures intermittentcooling is “B<P” as it is understood from FIG. 3.

By intermittent cooling, the surface temperature of a reduced-ironagglomerate 5 on a conveyer 6 lowers while changing for example as shownin FIG. 10. That is, the surface of the reduced-iron agglomerate iscooled with spray water ejected through the first spray nozzle 1,thereafter the surface temperature begins to rise due to the internalheat of the reduced-iron agglomerate during the time until the surfaceis cooled with the next spray water, and the surface temperature risestops at the time when the temperatures at the inside and the outside ofthe reduced-iron agglomerate balance with each other.

Then, next cooling is commenced from the balanced temperature with thenext spray water. By repeating such steps, the reduced-iron agglomerate5 is cooled to 100° C. to 300° C. in accordance with such a coolingpattern as shown in FIG. 10. In the case of intermittent cooling, sincethe temperature of a reduced-iron agglomerate 5 lowers by the giving andreceiving of heat in the agglomerate and the forced cooling with spraywater supplied from the outside, the unit consumption of water can bereduced in comparison with the case of continuous forced cooling.

The reason why cooling can be accomplished with a small unit consumptionof water is presumably that the internal transfer of heat in areduced-iron agglomerate is faster than that in the case of applyingspray water unilaterally from outside.

Further, in the case of the intermittent cooling of the reduced-ironagglomerate, the water sprayed on the surface thereof evaporates and thesurface dries due to the rise of the surface temperature between coolingand the subsequent cooling. By repeating such a pattern, the surface ofthe reduced-iron agglomerate is cooled to a target discharge temperaturewhile water spraying and evaporation are repeated alternately. By sodoing, the reduced-iron agglomerate 5 discharged from a coolingapparatus according to the present invention can have a water content of6% or less.

It is preferable that the water content of a reduced-iron agglomerate islow in order to reduce the energy consumption during melting in anelectric arc furnace or the like and a preferable water content is also6% or less in order to prevent a water vapor explosion at the time whenthe reduced-iron agglomerate is charged into molten metal.

A preferable temperature of a reduced-iron agglomerate at the time ofdischarge after cooling is in the range from 100° C. to 300° C. in thepresent invention. A reduced-iron agglomerate discharged from a rotaryhearth furnace at about 1,000° C. is cooled to a temperature in therange from 100° C. to 300° C. by intermittent water spray.

In the general arrangement of cooling nozzles, as shown in FIGS. 14 and15, cone spray nozzles are arranged so that water may be sprayeduniformly over the entire area in the width and conveying directions ofa reduced-iron agglomerate.

In this arrangement, the temperature difference between the interior andthe surface of a reduced-iron agglomerate (a high temperature at theinterior and a low temperature at the surface) increases due to thecontinuous water spray and a larger amount of water is required incomparison with the intermittent water cooling according to the presentinvention. When a water amount is increased in order to cool areduced-iron agglomerate sufficiently in the interior, water remains onthe surface that has already been cooled to a low temperature and thewater content exceeds 6%.

Further, when cone spray nozzles are used as shown in FIG. 14 or 15,overlaps are formed in the region 1-2 or 1-3 sprayed through eachnozzle, the cooling state varies in the direction of the width of aconveyer, and thus the temperature and the water content of areduced-iron agglomerate also vary.

The first cooling apparatus according to the present invention isconfigured so that the relation between the spread width of spray waterin the conveying direction “B” and the intervals of installed spraynozzles “P” may satisfy the aforementioned expression (2), namely1.2×B≦P≦10×B.

The condition “1.2×B≦P” is determined as the condition that makes surethat a sprayed range 1-1 is firmly separated from the sprayed range ofan adjacent spray nozzle 1 as shown in FIG. 2, namely the condition forthe assurance of intermittent cooling.

The condition “P≦10×B” is determined as the condition that makes surethat the temperature rise caused by the internal heat of a reduced-ironagglomerate is not saturated during the time between cooling and thesubsequent cooling and effective cooling is secured.

Next, the second cooling apparatus according to the present invention isconfigured so that the relation between the spread width of spray waterin the conveying direction “B” and the spread width thereof in theconveyer width direction “W” may satisfy the aforementioned expression(3), namely W≧2×B.

Under this condition, by employing, for example, flat spray nozzles thatmake the sprayed ranges 1-1 flat, the spread width of spray water in theconveying direction “B” is nearly constant in the conveyer widthdirection, therefore the variation of the cooling state in the conveyerwidth direction decreases, and resultantly intermittent cooling can becarried out effectively.

Further, the first and second cooling apparatuses according to thepresent invention are configured so that the relation between the spreadwidth of spray water in the conveyer width direction “W” and the widthof the conveyer “CW” may satisfy the aforementioned expression (5),namely CW≦W.

That is, by building up the relation between “W” and “CW” as shown inFIG. 4, it becomes possible to cool a reduced-iron agglomerate on aconveyer 6 uniformly in the conveyer width direction.

In FIG. 1, a reduced-iron agglomerate 5 discharged from a rotary hearthfurnace 13 is loaded continuously on a conveyer 6 and conveyed. Spraynozzles 1 are arranged above the conveyer 6 at prescribed intervals inthe direction of the conveyer traveling.

As a result, though water is sprayed continuously through each of thespray nozzles 1, the water is intermittently sprayed on the reduced-ironagglomerate 5 conveyed continuously on the conveyer 6. The coolingpattern of intermittent water spray as viewed from agglomerate is, forexample, as shown in FIG. 9, and the time durations of “on” and “off” ofthe water spray can be adjusted by the relation between “P” and “B”.

FIG. 11 shows another cooling apparatus according to the presentinvention. That is, a high-temperature reduced-iron agglomerate 5reduced in a rotary hearth furnace 13 is fed from an outlet 8 on aconveyer 6 in a cooling apparatus 16 installed in connection with theoutlet, cooled with water sprayed through a plurality of upper spraynozzles 1 and lower spray nozzles 1 a installed above and below theconveyer 6 while being conveyed, and then discharged from a reduced-ironagglomerate outlet 7.

In this way, a high-temperature reduced-iron agglomerate loaded on aconveyer 6 is cooled from top and bottom by a plurality of nozzles 1 and1 a installed above and below the conveyer 6. By so doing, it becomespossible to load a reduced-iron agglomerate in plural layers on aconveyer 6 and to improve productivity.

FIG. 12, like FIG. 4, shows the state of spraying water through spraynozzles 1 and 1 a installed above and below a conveyer 6 and FIG. 13,like FIG. 5, shows means 2, 2 a, 3 and 3 a for supplying water to upperand lower spray nozzles 1 and 1 a.

As a conveyer 6, a tabular type or a wire-gauze type conveyer is adoptedand, in the case where a reduced-iron agglomerate is cooled with nozzlesinstalled above and below a conveyer 6, a cooling efficiency furtherimproves when a wire gauze type conveyer 6 is adopted. Further, withregard to the size of the openings of the wire gauze, any size may beacceptable, as long as a reduced-iron agglomerate does not fall throughwhen it is loaded thereon, but a preferable size of the openings isabout 10 mm.

Another present invention is explained on the basis of the coolingapparatus shown in FIGS. 1 and 16.

FIG. 16 shows an example of a plan view taken on line A-A of FIG. 1 fromabove the conveyer 6. In the figure, the intervals “P” of spray nozzles1 are arranged so that “P” may equal to “B” and water ejected from eachof the spray nozzles 1 is sprayed so as to form the spread width in theconveying direction “B” as shown by the spraying range 1 a. Thisarrangement makes it possible for the spread widths of spray water inthe conveying direction “B” of adjacent nozzles 1 not to overlap witheach other.

FIG. 17 is an expanded sectional view taken on line C-C of FIG. 16. Inthe figure, each of the spray nozzles 1 is attached to a spray header 2at intervals “P” in the conveying direction and spray water is sprayedon a conveyer 6 so as to form the spread width in the conveyingdirection “B”.

Likewise, FIG. 4 is a front view taken on line B-B of FIG. 16. In thefigure, a spray nozzle 1 is attached to the spray header 2 disposed inthe center of the width direction of the conveyer 6 and spray water issprayed on the conveyer 6 so as to form a spread width in the widthdirection “W” that is larger than the width of the conveyer 6 “CW”.

Water is supplied to a spray header 2 through a feed water pipe 3 asshown in FIG. 1.

In the present invention, as explained above, a plurality of spraynozzles 1 are installed above a conveyer 6 at prescribed intervals inthe conveying direction, of the reduced-iron agglomerate 5, the relationbetween an ejecting time “T1” and an ejection stopping time “T2” of eachof the spray nozzles 1 is arranged to satisfy the expression“1.2×T1≦T1+T2≦10×T1” and the reduced-iron agglomerate 5 on the conveyeris cooled intermittently (on-off) as shown in FIG. 18.

By employing intermittent cooling, the surface temperature of areduced-iron agglomerate 5 on a conveyer 6 lowers while changing, forexample, as shown in FIG. 10. That is, by ejecting water through spraynozzles 1 for a time “T1” and stopping the water ejection for a time“T2”, the surface temperature of the reduced-iron agglomerate begins torise (heat recovery) due to the internal heat of the reduced-ironagglomerate during the ejection stopping time “T2” after cooled withspray water for the time “T1” and the surface temperature rise stops atthe time when the temperatures at the inside and the outside of thereduced-iron agglomerate balance with each other.

Then, the next cooling commences, from the balanced temperature, withthe next spray water. By repeating such steps, the reduced-ironagglomerate 5 is cooled to 100° C. to 300° C. in accordance with such acooling pattern as shown in FIG. 10. In the case of intermittentcooling, as the temperature of a reduced-iron agglomerate 5 lowers bythe giving and receiving of heat in the agglomerate and the forcedcooling with spray water supplied from the outside, the unit consumptionof water can be reduced in comparison with the case of continuous forcedcooling.

The reason why cooling can be accomplished with a small unit consumptionof water is presumably that the internal transfer of heat in thereduced-iron agglomerate is faster than that in the case of applyingspray water unilaterally from outside.

Further, in the case of the intermittent cooling of the reduced-ironagglomerate, the water sprayed on the surface thereof evaporates and thesurface dries due to the rise of the surface temperature between onecooling and the subsequent cooling. By repeating such a pattern, thesurface of the reduced-iron agglomerate is cooled to a target dischargetemperature while water spraying and evaporation are repeatedalternately. By so doing, the reduced-iron agglomerate 5 discharged froma cooling apparatus according to the present invention can secure awater content of 6% or less.

It is preferable that the water content of a reduced-iron agglomerate islow in order to reduce the energy consumption during melting in anelectric arc furnace, or the like, and a preferable water content isalso 6% or less in order to prevent water vapor explosion at the timewhen the reduced-iron agglomerate is charged into molten metal.

As shown in FIGS. 14 and 15, cone spray nozzles are generally used ascooling nozzles and arranged so that the spread of spray water ejectedthrough the cooling nozzles may interfere with each other over theentire area in the width and conveying directions of a reduced-ironagglomerate and thus the spray water may be sprayed on over all thereduced-iron agglomerate.

In this arrangement, the temperature difference between the interior andthe surface of a reduced-iron agglomerate (a high temperature at theinterior and a low temperature at the surface) increases due to thecontinuous water spray and a larger amount of water is required incomparison with the intermittent water cooling according to the presentinvention. When a water amount is increased in order to cool areduced-iron agglomerate sufficiently up to the interior, water remainson the surface that has already been cooled to a low temperature and thewater content exceeds 6%.

Further, when cone spray nozzles are used as shown in FIG. 14 or 15,overlaps are formed in the region 1-2 or 1-3 sprayed through eachnozzle, the cooling state varies in the direction of the width of aconveyer, and thus the temperature and the water content of areduced-iron agglomerate also vary.

Another cooling apparatus according to the present invention isconfigured so that the relation between an ejecting time “T1” and anejection stopping time “T2” of spray water may satisfy the expression1.2×T1≦T1+T2≦10×T1.

That is, the term “1.2×T1≦T1+T2” is the condition for securingintermittent cooling for a shortest time period in order to determine anejecting time and an ejection stopping time of spray water.

The term “T1+T2≦10×T1” is the condition for securing effective coolingwithout the saturation of a temperature rise caused by the internal heatof a reduced-iron agglomerate after cooling.

The third cooling apparatus according to the present invention isconfigured so that the spread width of spray water in the conveyingdirection “B” and the intervals of spray nozzles in the conveyingdirection “P” may satisfy the expression “B≦P”. The condition determinesthe intervals of spray nozzles 1 so that the spread widths of spraywater “B” ejected through the spray nozzles 1 may not overlap with eachother and, under this condition, uniform cooling is realized.

The fourth cooling apparatus according to the present invention isconfigured so that the relation between the spread width of spray waterin the conveyer width direction “W” and the spread width thereof in theconveying direction “B” may satisfy the expression “2B≦W”. Under thecondition, a spray region 1 a becomes flat as shown in FIG. 16.

For example, when flat spray nozzles are adopted, as the spread width ofspray water in the conveying direction “B” becomes nearly constant inthe conveyer width direction, the variation of the cooling state in theconveyer width direction decreases and resultantly intermittent coolingcan be carried out effectively.

Further, in the aforementioned third cooling apparatus according to thepresent invention, by configuring the cooling apparatus so that therelation between the spread width of spray water in the conveyer widthdirection “W” and the conveyer width “CW” may satisfy the expression“CW≦W”, namely by building up the relation between “W” and “CW” as shownin FIG. 4, a reduced-iron agglomerate on a conveyer 6 is cooleduniformly in the conveyer width direction.

EXAMPLES

Next, the results obtained from the examples of the present inventionare shown in FIGS. 6 to 8.

The intermittent cooling of the invention examples was performed underthe condition prepared so that the relation between the spread width ofspray water in the conveying direction “B” and the intervals of theinstalled spray nozzles “P” might satisfy the expression “2B=P” andunder this condition prepared so that the relation between the spreadwidth of spray water in the conveying direction “B” and the intervals ofthe installed spray nozzles “P” might satisfy the expression “B≦P” andthe relation between the spraying time and the spray stopping time mightsatisfy the expression “1.2×T1+T2”. The continuous cooling of thecomparative examples was performed under the condition of “B≧P”.

FIG. 6 shows the relationship between the temperature at the center of areduced-iron agglomerate during cooling and a spray water amount. It isunderstood that the intermittent cooling of the invention example isexcellent in cooling effect in comparison with the continuous cooling ofthe comparative example.

By the present invention, the temperature at the center of thereduced-iron agglomerate is lowered to preferably not higher than 300°C., as shown by the solid line, and still more preferably not higherthan 200° C., as shown by the broken line.

Further, whereas, in the case of the intermittent cooling of theinvention example, the temperature is 300° C. or lower when the relativespray water amount is 0.7 or more, in the case of the continuous coolingof the comparative example, the relative spray water amount of 2.0 isrequired.

FIG. 7 shows the relationship between a spray water amount and a watercontent after cooling. In the case of the intermittent cooling accordingto the present invention, it is possible to regulate the water contentof a reduced-iron agglomerate by the spray water amount. A preferablewater content is not more than 6% as shown by the solid line and stillmore preferably not more than 5%, as shown by the broken line.

In the case of the intermittent cooling of the invention example, thewater content is 6% or less when the relative spray water amount is 1.3or less and the temperature is 300° C. or lower and the water content is6% or less when the relative spray water amount is in the range from 0.7to 1.3. On the other hand, in the case of the continuous cooling of thecomparative example, the water content exceeds 6% when the temperatureis controlled to 300° C. or lower.

FIG. 8 is a graph obtained by putting FIGS. 6 and 7 together and showsthe relationship between the temperature at the center of a reduced-ironagglomerate and the water content thereof. In the case of the continuouscooling of the comparative example, the water content exceeds 6% whenthe temperature at the center of the reduced-iron agglomerate is loweredto 300° C. or lower and the temperature at the center exceeds 300° C.when the water content is controlled to 6% or less.

In contrast, in the case of the intermittent cooling of the inventionexample, as shown by the solid line, the temperature at the center andthe water content can be regulated to 300° C. or lower and 6% or lessrespectively and a good reduced-iron agglomerate can be obtained.

2) Another present invention is further explained on the basis of thecooling apparatus shown in FIG. 19.

The technological concept of the present invention is explainedhereunder.

Spray nozzles are arranged above a cooling conveyer along the conveyingdirection and a reduced-iron agglomerate is cooled with water sprayedfrom above. However, the bottom surface and the center portion of thereduced-iron agglomerate are hardly cooled with only the cooling fromabove.

Therefore, the temperature difference appears between the top and bottomsurfaces of the reduced-iron agglomerate and, when a spray water amountis insufficient, the heat at the bottom surface is transferred aftercooling and the cooling becomes insufficient.

On the other hand, when a spray water amount is abundant, waterpenetrates the top surface of a low temperature and the water contentincreases.

In this light, with intent to achieve both “cooling to a temperature of300° C. or lower at the center” and “a water content of 6% or less” atthe same time, the method is used wherein a reduced-iron agglomerate iscooled from the top and bottom surfaces by raising both the sideportions of a conveyer and accumulating cooling water so as to form awater layer 1 mm to less than 10 mm on the conveyer.

When water accumulates so as to form a water layer 1 to less than 10 mm(which corresponds to less than a half of the thickness of areduced-iron agglomerate) at the bottom of a conveyer by raising boththe side portions of the conveyer, the bottom surface of thereduced-iron agglomerate is cooled by the heat of the evaporation ofwater and the temperature difference between the top and bottom surfacesdecreases. Therefore, both “cooling to a temperature of 300° C. or lowerat the center” and “a water content of 6% or less” can be achieved atthe same time.

When a water layer at the bottom of a conveyer is less than 1 mm inthickness, the ability to cool the reduced-iron agglomerate isinsufficient. On the other hand, when it is 10 mm or more in thickness,a water content increases excessively. For that reason, the thickness ofa water layer is determined to be in the range from 1 mm to less than 10mm.

With regard to a method of spraying cooling water on a reduced-ironagglomerate through spray nozzles installed above a conveyer, thecooling water may be sprayed intermittently, instead of continuously, onthe reduced-iron agglomerate. By this intermittent cooling, it becomespossible to cool a reduced-iron agglomerate to a uniform temperaturefrom the surface to the center. The method of intermittent spraying isnot particularly specified and it is preferable to repeat spraying andnon-spraying during the course of cooling by adjusting the arrangementand the spread angle of spray nozzles.

The present invention is explained on the basis of FIGS. 19 and 20.

FIG. 19 shows the overall view of a cooling apparatus according to thepresent invention.

A high-temperature reduced-iron agglomerate is discharged from theoutlet 8 of a rotary hearth of a reduced-iron production equipment andloaded on a cooling conveyer 6. The temperature of the reduced-ironagglomerate discharged from the outlet 8 of the rotary hearth is 1,000°C. Spray nozzles 1 are installed above the cooling conveyer 6 andcooling water is sprayed on the reduced-iron agglomerate on the coolingconveyer 6 through the spray nozzles 1.

In such a cooling apparatus, when the length of the cooling conveyer 6is set at 6.5 m and the conveying speed at 6.5 m/min., the reduced-ironagglomerate is cooled for about 1 min. In the meantime, the reduced-ironagglomerate is cooled from about 1,000° C. to 300° C. or lower.

The cooled reduced-iron agglomerate is conveyed from the end of thecooling conveyer 6 as a product. Further, sludge formed during thecourse of cooling is separated from water at a shoot 18, thereafterrecovered with a sludge recovery conveyer 17, and reused as an ironsource. Here, vapor generated during the course of cooling is dischargedoutside through a vapor duct 4.

FIG. 20 shows the structure of a cooling conveyer 6. “W” in the FIG. 20shows the width direction of the cooling conveyer 6 and “L” the lengthdirection thereof. FIG. 20 shows a pallet of the cooling conveyer 6 andthe cooling conveyer 6 is composed of a series of the pallets in thelength direction.

Such side walls as shown in FIG. 20 are placed at both the sides of thecooling conveyer 6 and the structure is configured so that cooling watersprayed through spray nozzles 1 may not fall down from the sides of thecooling conveyer 6. Accordingly, a water layer 1 mm to not more than 10mm, in depth, can accumulate at the bottom of the cooling conveyer 6.

Further, the bottom plate 21 of the cooling conveyer 6 is made of asteel plate and the structure is configured so that the cooling watermay not fall down from the bottom plate 21.

EXAMPLES

The results of the examples according to the present invention are shownin FIGS. 21 and 22.

FIG. 21 is a graph showing the relationship between the spray amount ofcooling water and the temperature at the center of a reduced-ironagglomerate. The line indicated as the water depth of 2 mm representsthe case where the bottom plate 21 of the cooling conveyer 6 is made ofa steel plate and the line indicated as wire gauze (0 mm) represents thecase where the bottom plate of the cooling conveyer 6 is made of wiregauze. A spray water amount is expressed by a relative value obtained byregarding the calculated spray water amount required for cooling as 1.0.

As shown in FIG. 21, according to this example, in the case of using asteel plate as the bottom plate of the cooling conveyer 6 and forming awater layer 2 mm in depth, the temperature at the center of areduced-iron agglomerate can be lowered to 300° C. or lower when thespray water amount is about 1.1 times the calculated required amount.

On the other hand, in the case of using wire gauze as the bottom plateof the cooling conveyer 6, the temperature at the center of areduced-iron agglomerate can be lowered only to 470° C. even when thespray water amount is about 1.1 times the calculated required amount.

FIG. 22 is a graph showing the relationship between the spray amount ofcooling water and the water content of a reduced-iron agglomerate. Theviewpoint of the figure is the same as that of FIG. 21.

As shown in FIG. 22, according to this example, in the case of using asteel plate as the bottom plate of the cooling conveyer 6 and forming awater layer 2 mm in depth, the water content can be suppressed to 6% orless even when the spray water amount is increased to 1.5 times thecalculated required amount.

On the other hand, in the case of using wire gauze as the bottom plateof the cooling conveyer 6, the water content exceeds 6% when the spraywater amount exceeds the calculated required amount.

From the results shown in FIGS. 21 and 22, it can be understood that itbecomes possible that a temperature at the center of a reduced-ironagglomerate is 300° C. or lower and a water content is 6% or less byraising both the side portions of a cooling conveyer 6, using a steelplate as the bottom plate of the cooling conveyer 6 and forming a waterlayer 2 mm in depth.

INDUSTRIAL APPLICABILITY

By a method and an apparatus according to the present invention, it ispossible to cool a high-temperature reduced-iron agglomerateintermittently, to cool it effectively to a temperature in the rangefrom 100° C. to 300° C. at a breath and, as a result, to suppress thereoxidation caused by the atmospheric air.

Further, it is possible to regulate the water content of a cooledreduced-iron agglomerate to 6% or lower, to eliminate the danger of awater-vapor explosion at the time when the reduced-iron agglomerate ischarged into molten metal, and also to suppress the energy required formelting.

Further, the present invention makes it possible to reduce a watercontent to 6% or less in comparison with an immersion cooling method andtherefore to suppress the pulverization and the reoxidation.Furthermore, by the present invention, a conveyer itself is also cooledand, therefore, the durability of the conveyer is improved.

1. A method for cooling a reduced-iron agglomerate in a reduced-ironagglomerate production equipment wherein an iron oxide agglomerate isreduced in a reducing furnace and discharged as a reduced-ironagglomerate characterized by: installing a conveyor to convey saidreduced-iron agglomerate at the outlet of said reduced-iron agglomerateproduction equipment; installing a plurality of spray nozzles above saidconveyor at intervals (P) satisfying the expression 1.2×B≦P≦10×B, whereB is the spread width of spray water in the conveying direction, so thatspread widths of spray water in the conveying direction of saidreduced-iron agglomerate do not overlap with each other; setting thespread width of spray water in the conveying direction B and the spreadwidth thereof in the conveyor width direction W satisfying theexpression: W≧2×B, where W is the spread width of spray water in theconveyor width direction and B is the spread width of spray water in theconveying direction; cooling said reduced iron agglomerate on saidconveyor intermittently by ejecting cooling water intermittently throughsaid spray nozzles so that an ejecting time T1 and an ejection stoppingtime T2 satisfy the following expression:1.2×T1≦T1+T2≦10×T1; where T1 is an ejecting time and T2 an ejectionstopping time; to lower a surface temperature by repeated cycles ofrising and lowering of the surface temperature of said reduced-ironagglomerate; providing side portions arranged on said conveyor, saidside portions accumulating said cooling water and forming a water layer1 mm to less than 10 mm in depth on said conveyor; said cooling of saidreduced-iron agglomerate being a rapid cooling to a temperature range of100° C. to 300° C. thereby suppressing reoxidation by atmospheric air;regulating water content of said reduced-iron agglomerate after coolingto 6% or less.